.*. •-*
Power for
Preliminary Description of the Bristol Proteus Turboprop
Unit : Brabazon and S.R.45 Coupled Installations in Detail
MATCHING in magnitude the structural and aero-dynamic problems which attend the BristolBrabazon I Mark II, landplane and Saunders-Roe
S.R.45 flying boat is the task of providing power units for
these civil colossi. This can well be appreciated when it is
considered that the respective all-up weights will be 130 tons
and 135 tons, and that a very high speed and long range
is' demanded in both instances. Official restrictions have
hitherto precluded any detailed appreciation of power plant
features, but the release of preliminary information on the
Bristol Proteus turboprop now permits description and
illustration of how power is being provided by the Engine
Division of the Bristol Aeroplane Co., Ltd., and of the
manner in which this will be utilized by the airframe
designers. Both the Proteus itself and the coupled instal-
lation will, we believe, be judged worthy of the Brabazon
and S.R.45 designs.
Though in the first instance the Brabazon I is to be air-
tested with an installation of coupled Bristol Centaurus
reciprocating engines (see Flight, December 26th, 1946),
subsequent machines will each receive four coupled pairs of
Model of the coupled Proteus installation for the Brabazon.
Proteus. The S.R.45 W*U b* powered from the outset with
ten Proteus units—four in coupled pairs and two individual
units outboard. Before surveying the coupled installa-
tion, common to both aircraft, all available information on
the Proteus itself will be presented, together with some
account of development to date.
The Proteus—a unit of roughly 3,500 h.p.—was started
up for the first time on January 25th, 1947. Valuable data
had already been gained from the testing of the smaller
Theseus unit of about 2,300 h.p., which first ran on July
18th, 1945, and which, by December of the following year,
had successfully completed the Ministry of Supply 1 oo-hour
type test. In Lincoln aircraft the Theseus has since amassed
over 600 flying hours and, as lately described in Flight,
has completed an arduous 500-hour endurance test, during
which all major items were sealed.
Though certain design techniques are expressed both in
the Theseus and Proteus, the latter unit differs considerably
in layout. The compressor is a combined axial and centri-
fugal unit, centrally located and having the combustion
chambers disposed around it. Photographs and drawings
A MATTEJl OF NOMENCLATURE
O all but students of Greek mythology the name
Proteus will be unfamiliar and its suitability to the
new Bristol turboprop' unit not, perhaps, apparent.
The adjective " protean," meaning variable, certainly
does not help to elucidate the matter.
Editorial research discloses that the divinity concerned
may have personified the changeable aspect of the sea,
and that be held the secret of contrary winds. This
knowledge lends a special Interest to the terms of the
Brabazon and S.R.45 specifications which demand
exceptionally long ranges in face of perverse winds.